Diclofenac is a nonsteroidal anti-inflammatory drug (NSAID) which provides anti-inflammatory, analgesic, and antipyretic activity in humans. Salts of diclofenac, benzeneacetic acid derivatives, are designated chemically as 2-[(2,6-dichlorophenyl)amino] benzeneacetic acid salt. A delayed release formulation of diclofenac, Voltaren.TM. Delayed release, has been developed and utilizes diclofenac sodium salt in an enteric coated tablet which acts to resist the release of diclofenac in the low pH of gastric fluid, however, it allows rapid release of drug in the higher pH of the duodenum.
As understood in the prior art, enteric coatings are not an efficient method for the delivery of NSAIDs such as diclofenac due to the inability of such coating systems to provide or achieve a sustained therapeutic effect due to the lack of prolonged release of the pharmaceutical agent with only a single dose over a long period of time. Enteric coats are designed to dissolve or breakdown in an alkaline environment. The presence of food may increase the pH of the stomach. Therefore, the concurrent administration of enteric coated diclofenac with food or the presence of food in the stomach may lead to dose dumping and unwanted secondary effects. Furthermore, given the fact that NSAIDs can cause stomach irritation and sometimes peptic ulceration and gastrointestinal bleeding, it would be desirable to have a drug delivery system that is capable of providing the controlled delivery of diclofenac or other pharmaceutically acceptable salts of diclofenac in a predictable manner over a long period of time.